Hitherto, a gap between members formed in constructs such as buildings, vehicles, electronic devices is filled with a sealing material, to provide water cut-off, heat insulation and sound absorption. Foams made of synthetic resins or rubbers are used for the sealing materials. The foams have appropriate repulsive force (compression stress). Therefore, the foams adhere, due to compliance, to the irregularity on the surface of the members to be sealed, under application of small compression deformation. Accordingly, an excellent seal property can be attained.
Above all, a rubber foam obtained by expanding ethylene-α-olefin-diene copolymer rubber foam by using a blowing agent such as azodicarboxylic amide is preferably used as a sealing material, because of excellent weather resistance, heat resistance and seal properties (Patent Literature 1 and 2). In the rubber foam, small cell diameter, appropriate expansion ratio and compression stress are effective for improving the properties required to the foam (water cut-off property, heat insulation property, sound absorption property, etc). Therefore, the rubber foam is subjected to bubble control by use of a treatment/processing auxiliary such as stearic acid.